VET-114 Animal Anatomy and Physiology 2 Lesson 3 Digestive and Endocrine Systems Chapters 11, 12, 15 The Digestive System Chapter 11 Pages 264-282 Textbook Learning Objectives Chapter 11 – Page 264 • List the functions of the digestive system. • Describe the epithelial and muscle layers of the gastrointestinal tract. • Explain the process of peristalsis. • List the structures of the oral cavity. • List and give the locations of the salivary glands. • Name the types of teeth found in carnivores and herbivores and describe the structure of teeth. • Differentiate between mechanical and chemical digestion. • List the structures that make up the monogastric stomach and describe the function of each area. • Explain the effect(s) on the gastrointestinal system of amylase, lipase, gastrin, pepsin, pepsinogen, prostaglandins, mucin, bicarbonate, secretin, cholecystokinin, proteases, and hydrogen and chloride ions. • Describe the structure and functions of the rumen, reticulum, omasum, and abomasum. • Differentiate between fermentative and nonfermentative digestion. • List the segments of the small and large intestine and describe the general functions of each segment. The Digestive System • Gastrointestinal tract (GIT) • Alimentary canal Putting Things in Perspective! VERY important system clinically! The “Tracts” of Internal Medicine The Digestive System (GIT) Figure 11-1, Page 265 • Digestive tract, gastrointestinal (GI) tract, alimentary canal, gut • Tube that runs from the mouth to the anus; accessory digestive organs Basic Functions of GIT Digestion of Macronutrients Absorption of All Nutrients Elimination of Wastes Digestion of Macronutrients • Definition – large nutrient molecules that require breakdown into smaller molecules before being absorbed . “Energy” nutrients (Calories) . Carbohydrates . Fats . Proteins Digestion of Macronutrients Absorption of All Nutrients • Macronutrients • Micronutrients – nutrient molecules so small that no digestion is required before being absorbed . Vitamins . Minerals . Water Elimination of Wastes • Food – • Chyme – • Feces – waste product from animal's digestive tract expelled through the anus during defecation . Water (75%) . Bacteria . Fiber . Undigested/unabsorbed nutrients . Waste products Comparative A&P Herbivores Carnivores Omnivores Species Variation • Requirements for digestion and absorption of foodstuffs vary depending on diet of animal . Herbivores – plant-eating animals (cattle, sheep, goats) . Carnivores – meat-eating animals (cats) . Omnivores – animals that eat plant material and meat • Monogastric animals – simple, single stomachs • Ruminants – multiple mixing and fermentation compartments in addition to stomach Herbivores Carnivores Omnivores Anatomy of GIT Trace a Bolus of Food from the Oral Cavity to the Anus 3 Tracts Exiting Body Trace a Bolus of Food Figure 11-1, Page 265 Digestive Tract Structure Figure 11-2, Page 266 • Mucosa – lining of GI tract; epithelium and loose connective tissue • Submucosa – dense connective tissue; may contain glands • Muscle layer – outside the submucosa • Serosa – outermost layer; thin, tough connective tissue. Mesentery • Sheets of connective tissue • Suspend digestive tube in abdomen from dorsal body wall • Contains blood and lymph vessels and nerves that supply GI tract Digestive Tract Epithelium • Stratified squamous epithelium . Thick and tough . Lines the mouth, pharynx, esophagus, and anus • Simple columnar epithelium . Runs from junction of esophagus and stomach through the intestines to junction of rectum and anus . Nutrients are absorbed through this thin epithelium Digestive Tract Musculature • Skeletal muscle – voluntary control . Mouth, pharynx, the cranial part of the esophagus, and the external anal sphincter . Allows the processes of chewing, mixing saliva with food, and initiation of swallowing • Smooth muscle – involuntary control . Wall of the majority of the esophagus, the stomach, the small intestine, the large intestine, and the internal anal sphincter Peristalsis Figure 11-3A, Page 267 • Circular muscle contractions • Wavelike movement along the tract • Propel digestive tract contents along the tube ahead of them Segmental Contractions Figure 11-3B, Page 267 • Periodic circular muscle contractions • Occur in different adjacent sites • Mixes digestive tract contents and slows their movement through the tract Mouth Oral cavity Buccal cavity Mouth (Oral Cavity) • Lips • Salivary glands • Tongue • Teeth • Hard palate • Soft palate Salivary Glands • Exocrine glands • Produce saliva; usually three pairs with ducts that carry the saliva to the oral cavity . Parotid salivary glands – ventral to the ear canals . Mandibular salivary glands – ventral to the parotid glands at the caudal angle of the mandible . Sublingual salivary glands – medial to the shafts of the mandible just under the base of the tongue Oral Cavity Functions • Lips may play role in prehension • Initiate mastication (mechanical digestion) . Breaks food into smaller particles that increase the surface area available for exposure to the enzymes involved in chemical digestion • Initiate chemical digestion . Saliva – added to food as it is chewed; moistens, softens, and shapes food into a form that is more readily swallowed . Salivary amylase Comparative Anatomy Tongue Figure 14-2, Page 343 • Tongue has 4 types of taste buds Teeth • Mastication – chewing; physically break down food into smaller pieces • Upper arcade – contained in maxilla and incisive bones • Lower arcade – contained in mandible Teeth Shape Figure 11-4, Page 268 • Carnivore teeth – more pointed on their occlusal surface; slightly curved toward back of mouth . Good for holding prey, tearing, cutting, shredding • Herbivore teeth have flat occlusal surfaces . Good for grinding plant and grain material Types of Teeth Incisors Canines Premolars Molars Types of Teeth Figure 11-5, Page 268 Tooth Terminology • Lingual – inner surface of the lower arcade of teeth • Palatal – inner surface of the upper arcade • Labial – outer surface of the upper and lower arcade at the front the mouth • Buccal – outer surface of the teeth more caudal in the mouth Maxilla & Mandible • Tooth Surfaces . Lingual . Palatal . Labial . Buccal Dental Formula • Represents the typical number of each type of tooth found in the upper and lower arcade • Tooth type designated I for incisor, C for canine, P for premolar, and M for molar . Upper case for adult teeth . Lower case for deciduous teeth Dental Formula • Tooth type followed by two numbers separated by a slash mark or expressed as a fraction of one number over the other . First number – number of teeth in half of the upper arcade . Second number – number of teeth in half of the lower arcade • Total number determined by summing all the numbers and multiplying by 2 Dental Formulas Table 11-1, Page 269 Bassert Lab Manual – Page 274 48 Canine Mouth Canine Dental Formula Incisors Figure 11-5, Page 268 • Grasping teeth • Most rostral teeth of upper and lower arcade Canines • Tearing teeth • Located at corners of incisors • Longer than other teeth • Pointed at tip Premolars • Cutting teeth • Rostral cheek teeth • Sharp points and surfaces in carnivores Molars • Grinding teeth • Caudal cheek teeth • Larger, flatter occlusal surfaces • Used for grinding Dentition of a Cat Bassert Lab Manual – Page 272 Feline Dental Formula Comparative Anatomy Dog & Cat Upper Arcade Dog & Cat Lower Arcade – Dog & Cat Comparative Anatomy – Ruminants • Ruminants have no upper incisors or upper canine teeth . Dental pad – flat thick connective-tissue structure on the maxilla opposite the lower incisors and canine teeth Horse Teeth Comparative Anatomy Bird Beak Structure of Teeth Figure 11-6, Page 269 • Crown . Enamel . Dentin . Pulp • Gingiva • Root . Dentin . Pulp . Cementum . Periodontal ligament Crown • Enamel – covers crown of tooth . Hardest, toughest tissue in body • Pulp – center of tooth . Blood and nerve supply enter at apex of tooth root • Dentin surrounds and protects tooth pulp Gingiva • Epithelial tissue that composes gums around teeth • Gingival sulcus . Between crown and gingiva Root • Periodontal ligament • Cementum – hard connective tissue . Covers tooth root . Helps fasten tooth securely in its bony socket Dental Care • Clinical Application – . Page 270 Needs a Dentist? Dental Pathology Equine; Canine Dental Procedure Into the Abdomen Fun Comparative Anatomy! Esophagus & Stomach Food Becomes Chyme Esophagus • Transports swallowed material from pharynx to stomach • Enters the stomach at an angle in cardia region . Surrounded by cardiac sphincter muscle • As stomach expands, fold of the stomach against esophagus closes the lower end of esophagus . Reduces the risk for reflux . In some species, the closure is strong enough to prevent reflux or vomiting (horse, rabbit) Monogastric Stomach Figure 11-7, Page 271 • Five different areas 1. Cardia 2. Fundus 3. Body 4. Pyloric antrum 5. Pyloris Monogastric Stomach • Cardia – opening from the esophagus • Fundus – distensible blind pouch; expands as more food is swallowed • Body – distensible middle section . Fundus and body contain numerous glands . Gastric glands contain: •Parietal cells – produce hydrochloric acid •Chief cells – produce the enzyme pepsinogen •Mucous cells – produce the protective mucus Monogastric Stomach • Pyloric antrum – grinds up swallowed food; regulates hydrochloric acid . Glands contain G cells - secrete gastrin • Pylorus – muscular sphincter; regulates the movement of chyme from the stomach into the duodenum . Prevents